If it is made into a film, it will be nothing like the games. Thankfully, that would be a good thing, because a carbon copy of Half-Life would suck as a film.
However, this is Hollywood. They will fuck it up in plenty of other ways.
Also, while I agree on all the mute protagonist comments, realize it doesn't have to feature Gordon Freeman at all. The film could be the struggle against the Black Mesa forces by resistance fighters. There would of course be one or two main protagonists, but they would be speaking roles. If you think about it, one man--Gordon Freeman--could not possibly have taken down such a vast expansive force on his own. There were other battles raging elsewhere, and the film may just as well depict that aspect of the conflict.
It could be cool. I won't cast this one aside just yet.